Dye compositions have been applied in the past to fabrics and garments using numerous procedures. With the advent of high-boiling solvent dispersions, for instance substantially non-aqueous systems containing a solvent with a boiling point greater than that of water and of the aromatic ester or cycloaliphatic diester type as disclosed, for instance, in U.S. Pat. No. 4,293,305 (Wilson) as well as others, special requirements must be satisfied. It has been found that the elevated temperatures used in dyeing with the non-aqueous high-boiling solvent dispersions facilitate level fabric dyeing by swelling the synthetic fibers and relieving the heat history characteristics of the fabric. Non-contact means of applying dyes dispersed in high-boiling solvent to the fabric while the fabric is on width-holding chains are needed to allow simultaneous dyeing and heatsetting of the fabric. This is particularly the case since the high-boiling solvent dispersions are designed to operate most efficiently at elevated temperatures. Application of the dye dispersion at elevated temperatures while the fabric is under tension in a heated atmosphere allows for the simultaneous dyeing of the fabric and heatsetting the goods in open width.
Prior procedures for applying dyes in high-boiling solvent dispersions in open width have included dipping the fabric in a tank filled with the hot dye dispersion. This method requires large volumes of dye and, over a period of time, the dye becomes exhausted from the pad bath as evidenced by shade changes that occur during the dyeing run. Another proposal is to flood the fabric with recirculated dye dispersion; this procedure also has difficulties, namely the need for large volumes of the solvent dispersions, which solvents are relatively expensive, as well as dye exhaust problems during operation. As described in U.S. Pat. No. 4,550,579 to Clifford, a constantly moving thin film flowing very rapidly is directed over a shaped article, not goods in open width. This procedure is said to allow continuous exposure of the shaped article, such as a finished garment, to fresh dye composition to keep the article to be dyed in contact with the dye composition throughout the entire dyeing process. The dyeing process is conducted at a substantially uniform temperature. A non-reactive environment is also provided to surround the the film dye bath to prevent degradation of the dye composition. This patent cautions that spray or shower techniques permit dye degradation when a sprayed dye-containing composition is exposed to the surrounding ambient atmosphere, allows for significant heat loss (where the dye composition is itself heated), and at elevated temperatures may cause significant dye degradation due to mixing with the ambient air.
U.S. Pat. No. 4,055,971 to Hermes describes a closed cycle dyeing, washing and solvent recovery apparatus in which a textile material is dyed in an enclosed chamber using a glycol as the high-boiling organic liquid. As depicted in the drawings, the dyestuff material, consisting of a dye plus high-boiling solvent, is applied to the cloth using a contact method (pad bath) outside of the chamber then led through the enclosed chamber through a tortuous path on a series of rolls.
High-boiling solvent dispersions have specific requirements not shared with aqueous-based systems. Thus, for aqueous systems, non-contact applicators, such as spray nozzles or a dyebath cascade are unsuited, according to conventional wisdom, because the dye-containing composition is applied unevenly to the fabric and a streaked, moire-dyed fabric results. We have found a dyeing process that is forgiving in that it permits uneven dye dispersion application, i.e., areas of fabric that are not completely contacted with the dye dispersion and areas of fabric that receive excessive dye dispersion, yet a level shade almost invariably results. These dye-containing liquids are correctly termed dispersions since only a fraction of the amount of dye normally used is truly soluble in the hot high-boiling solvent under operating conditions.
It is an object of the present invention to dye and heatset flat goods simultaneously and to utilize the advantages attendant on dyeing at high temperatures. The process takes full advantage of applying high-boiling solvent dispersions in a hot environment while the fabric to which these hot dispersions are applied is held in open width under tension. The process allows for careful control of the fabric wet pick-up, that is the amount of solvent dispersion provided to the fabric; the level of tension applied across the width of the fabric; and control of the level of dyeing of the fabric. Unlike previous proposals which require large quantities of solvent dispersion, the procedure described in more detail below allows for rapid color changes as well as for changing the width at which the high-boiling solvent dye dispersion is applied to accommodate changes in fabric width.
The invention is a continuous process for simultaneously uniformly solvent dyeing and uniformly heatsetting a fabric in open width at an elevated temperature in a closed environment. The process is conducted in a heated, enclosed chamber such as a tenter frame which holds fabric by the edges in open width. The chamber includes a dye applicator for applying a dyestuff-containing dispersion directly to the fabric without the applicator directly contacting the fabric, and a conveyor to move the fabric through the chamber.
The fabric is supplied in open width and passed through the heated, enclosed chamber while adjusting the fabric width, as required, as the fabric passes through the chamber. A heated dispersion of a dyestuff dispersed in a non-aqueous, high-boiling solvent is applied to the fabric while in open width in the heated chamber where the fabric is exposed to heat while the dye dispersion is in contact with the fabric. This allows the dye dispersion to migrate, penetrate thoroughly through the fabric and level substantially simultaneously uniformly dyeing and uniformly heatsetting the fabric. The heatset and dyed fabric is Then removed from the chamber and washed to remove residual solvent.